The present invention relates to a sheet supplying device including delivering means for delivering sheets one by one and feeding means for feeding the delivered sheet to a sheet processing portion, and relates to a sheet processing device using the sheet supplying device.
A sheet processing device for processing the supplied sheet in a sheet processing portion such as an image forming station is used in a recording device (printer) which is an information output device of a personal computer or the like, and the sheet processing device includes delivering means for delivering the sheets one by one and feeding means for feeding the delivered sheets to the processing portion.
Conventionally, sheet supplying devices for feeding the sheets one by one from a stack of sheets are widely known, and are used in printers, copying machines, facsimile machines and other recording devices. Generally, such a sheet supplying device comprises stacking means for stacking the sheets, delivering means for separating and delivering the stacked sheets one by one, and sheet detecting means for detecting a leading end or a trailing end of the delivered sheet, and feeding means for feeding the delivered sheet to the processing portion such as the image forming station or the like. The sheet detecting means includes an actuator (swing lever, for example) which is operated by abutment of the leading end of the delivered sheet thereto to block or open an optical path of a sensor (photo-interruptor), so that electrical signal of the sensor is rendered on and off in response to presence and absence of the sheet, respectively.
The separation and delivery of the sheet by the delivering means is ordinarily as follows. First, the sheet is singled out of the stack of sheets by a pick-up roller and a separating mechanism. Then, the leading end of the sheet is detected by the sheet detecting means. On the basis of the output of the sheet detecting means (leading end detection information), the delivering means delivers the sheet to the feeding means in a manner matching various delivery conditions. Thereafter, the feeding means feeds the sheet to the downstream, and feeds it through the sheet processing portion such as the image forming station or the like. During the feeding, a trailing end of the sheet is detected by sheet detecting means (sheet end detecting means), and the sheet is further fed by a predetermined distance.
FIG. 6 is a longitudinal sectional view of a sheet supplying device of a conventional recording device. FIG. 7 is a longitudinal sectional view of the sheet supplying device of FIG. 6 in a state at an instance of detecting the leading end of the sheet. FIG. 8 is a partial enlarged major part longitudinal sectional view of a major part of the sheet supplying device of FIG. 6. In FIGS. 6 and 7, the sheet P delivered by an unshown delivering means is fed through a feeding passageway T defined as a predetermined gap by a pinch roller holder 305 and a platen 303. In the feeding passageway, there is provided a detecting lever 307 as if it blocks the passing of the sheet. A leading end of the delivered sheet P contacts (abuts) to the detecting lever 307 (actuator) to rotate the detecting lever, which blocks or opens, by the other end portion thereof, the optical path of the sensor 308 in the form of a photo-interruptor mounted on the electrical substrate 102. The position of the leading end of the sheet is detected by changes of the output signal of the photo-interruptor.
More particularly, the delivered sheet P is caught by a nip N provided by the feeding roller 302 and the pinch roller 304 contacted thereto. The position of the nip N is taken as a reference position, and the position of the leading end of the sheet P is determined on the basis of the design positional relations among the detecting lever 307, the sensor 308 and the nip. When a distance between the nip N and a sheet contact position of the detecting lever at the instance of actuation of the photo-interruptor 308 by rotation of the detecting lever 307 of the actuator about the pivot 307c, is L, the position of the leading end of the sheet P is upstream of the nip N by the distance L at the instance when the photo-interruptor 308 is rendered on (open). When the sheet P is fed through the feeding passageway T defined by the platen 303 and the pinch roller holder 305, the sheet is guided along the platen 303 defining the lower surface of the feeding passageway T because of the influence of the gravity and the influence of the rigidity of the sheet.
In FIG. 7, the time when the detecting lever 307 crosses the optical axis of the photo-interruptor (sensor) (when the optical path is changed from the blocked state to the open state) is the time when the position of the leading end of the sheet P is detected. The position of the leading end of the sheet known to the main assembly of the apparatus is the position which is upstream of the nip N by the distance L. As shown in FIGS. 7 and 8, the sheet leading end contactable region 307b of the detecting lever 307 to which the leading end of the sheet is abuttable upon the detection is inclined from an upstream side toward a downstream side with respect to a downward direction.
With this structure, when the sheet shown by a solid line P1 in FIG. 8 is fed along the platen 303 which is the lower end surface of the feeding passageway, the situation is the same as that of the design, and therefore, the position of the leading end of the sheet can be detected correctly. However, the leading end portion of the sheet may be curled upwardly, or the leading end portion of the sheet may be waved under a high humidity ambience. In such a case, as shown by a broken line P2 in FIG. 8, the sheet may be fed along the pinch roller holder 305 defining the upper end surface of the feeding passageway, and therefore, a deviation arises between the position of the leading end of the sheet sensed by the device and the actual position of the leading end of the sheet, the deviation being δL=M−L. If this arises, the top position of the image formation may be inaccurate, or the top margin may be deviated from the intended margin, with the result of deterioration of the accuracy of the sheet processing such as image formation or the like on the sheet.
In some sheet supplying devices, the sheet is fed into the image forming station 401 without correcting obliqueness of the delivered sheet by the nip N between the feeding roller 302 and the pinch roller 304 after the leading end of the sheet is detected, and in the other supplying device, the sheet is fed into the image forming station with the obliqueness of the delivered sheet corrected. In the image forming station 401, there is provided a carriage portion 403 including a carriage 404 reciprocable in the main scan direction along a guiding shaft 405 and a recording head 402 carried on the carriage, and the image formation is effected on the sheet P by driving the recording head on the basis of image information. The sheet on which the image has been formed is discharged in the direction indicated by an arrow A by a sheet discharge portion 501 constituted by sheet discharging rollers 502, 503, spurs 504, 505 and so on.
In an example of obliqueness correcting mechanism, the leading edge of the sheet is abutted to the nip where the feeding means 302, 304 are not rotated, and the sheet is pushed by a predetermined degree, 3 mm, for example, thus forming a loop of the sheet to make the entirety of the leading edge of the sheet abuts the nip. Therefore, when the obliqueness correction is not carried out, the above-discussed deviation δL of the leading end position of the sheet results in the top margin deviation as it is in the print. On the other hand, when the obliqueness correction is carried out, the actual sheet pushing degree for the correction is deviated by δL from the proper degree of pushing, and therefore, the loop degree may be improper, resulting in deterioration of the obliqueness correction performance.